FreeBSD Manual Pages

CLOSE(2) FreeBSD System Calls Manual CLOSE(2)
NAMEclose -- delete a descriptor
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS#include <unistd.h>
intclose(intd);
DESCRIPTION
The close() call deletes a descriptor from the per-process object refer-
ence table. If this is the last reference to the underlying object, the
object will be deactivated. For example, on the last close of a file the
current seek pointer associated with the file is lost; on the last close
of a socket(2) associated naming information and queued data are dis-
carded; on the last close of a file holding an advisory lock the lock is
released (see further flock(2)). However, the semantics of System V and
IEEE Std 1003.1-1988 (``POSIX.1'') dictate that all fcntl(2) advisory
record locks associated with a file for a given process are removed when
any file descriptor for that file is closed by that process.
When a process exits, all associated file descriptors are freed, but
since there is a limit on active descriptors per processes, the close()
function call is useful when a large quantity of file descriptors are
being handled.
When a process forks (see fork(2)), all descriptors for the new child
process reference the same objects as they did in the parent before the
fork. If a new process is then to be run using execve(2), the process
would normally inherit these descriptors. Most of the descriptors can be
rearranged with dup2(2) or deleted with close() before the execve(2) is
attempted, but if some of these descriptors will still be needed if the
execve fails, it is necessary to arrange for them to be closed if the
execve succeeds. For this reason, the call ``fcntl(d, F_SETFD,
FD_CLOEXEC)'' is provided, which arranges that a descriptor will be
closed after a successful execve; the call ``fcntl(d, F_SETFD, 0)''
restores the default, which is to not close the descriptor.
RETURN VALUES
The close() function returns the value 0 if successful; otherwise the
value -1 is returned and the global variable errno is set to indicate the
error.
ERRORS
The close() function will fail if:
[EBADF] D is not an active descriptor.
[EINTR] An interrupt was received.
SEE ALSOaccept(2), execve(2), fcntl(2), flock(2), open(2), pipe(2), socket(2),
socketpair(2)STANDARDS
The close() function call is expected to conform to ISO/IEC 9945-1:1990
(``POSIX.1'').
HISTORY
A close() function call appeared in Version 7 AT&T UNIX.
FreeBSD 5.0 April 19, 1994 FreeBSD 5.0